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Cat 310 lost pressure

Jerry33

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Head scratcher; over 30 years experience but never had a problem like this. One cat 310 lost pressure to a Self Service bay so began the troubleshooting. The pump ran smoothly but would not build pressure both cold and hot were about 300 psi; low pressure was fine so no blockage in the bay; water pressure is great and all other bays are working great. Rinse is ok but hot water functions (soap and wax) are less than city water pressure; Everything checked out ok so decided to swap out a pump and now have the same results; Searched this forum and only thing I found was about check valves and I've eliminated or replaced all. Here's what I've done so far:
- Put in a new motor
- took the high pressure bay hose loose and connected a short hose to direct spray out of the pump room. this eliminated any problem in the bay
- by passed all check valves and even changed out the one from the HW tank
- eliminated the solenoid valves attached to the motor, one at a time. Asco Valves so just took the guts out to test. Then made sure the lines to the tank were clean.
- replaced the solenoid (cold water rinse) and even bypassed it
- Took the valves out and they look like new (the replacement pump was one removed from service and had been in storage but same problems existed with 1st pump)
- Used air hose to clear the wax and soap lines - no problem found
- checked flow from hot water tank and cold water supply, both ok
- the pump runs smoothly, like a new one; RPM of 5 HP 3 phase motor looks same as other motors;
- pump does not hesitate, cough, or sputter when switching from rinse to hot water function
- I don't have a nozzle on the test hose but the cold water shoots a strong stream while the hot water functions drops to a very weak stream
So what am I overlooking.
thanks, Jerry
 

MEP001

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Did you check the tip or the regulator or the spot free check valve?
 

Randy

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WOW! Looks like you've done just about everything but change out the hoses from water tanks to the pump, I'd change the hoses from the tank to the pump.
 

MEP001

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If the hose from the tank to the pump was bad, the pump would cavitate on soap and wax but not rinse.
 

JMMUSTANG

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I would disconnect the hose line going to the bay and hook another hose to the pump directly.
Turn on the pump and see if it works.
 

Randy

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I would disconnect the hose line going to the bay and hook another hose to the pump directly.
Turn on the pump and see if it works.
He's already done that. But without a nozzle on the hose. Jerry put a gun and nozzle on the hose you put directly on the pump.
 

Jerry33

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Did you check the tip or the regulator or the spot free check valve?
thanks. changed both the tip and the regulator and I don't have spot free but I've replaced and bypass or pinched off (like the weep) all check valves and removed the hose to the bay and put on a short temp hose. I admit that I didn't put a tip on the temp hose and will do that tomorrow to see if that will change things.
 
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Jerry33

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WOW! Looks like you've done just about everything but change out the hoses from water tanks to the pump, I'd change the hoses from the tank to the pump.
thanks. I disconnected the hosed and blew them out, at least back into the tank so they are open
 

Jerry33

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If the hose from the tank to the pump was bad, the pump would cavitate on soap and wax but not rinse.
And that is not happening. Pump runs smoothly when I change the functions
 

Jerry33

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I would disconnect the hose line going to the bay and hook another hose to the pump directly.
Turn on the pump and see if it works.
Thanks. I did that. Hose is now disconnected and temp hose connected.
 

Jerry33

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He's already done that. But without a nozzle on the hose. Jerry put a gun and nozzle on the hose you put directly on the pump.
Thanks. I will do that in the morning. Worked all day on it.
 

MEP001

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It can't be voltage. It would either affect all the bays and other equipment, or more likely it would just trip the breaker or thermal overload.

Have you checked or replaced the low pressure seals? The pump can draw air in through bad seals and won't cavitate. Rinse water coming in under pressure will stop the air draw.
 

Jerry33

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It can't be voltage. It would either affect all the bays and other equipment, or more likely it would just trip the breaker or thermal overload.

Have you checked or replaced the low pressure seals? The pump can draw air in through bad seals and won't cavitate. Rinse water coming in under pressure will stop the air draw.
No, I have not and that is a possibility. Thanks.
 

Randy

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Whatever it is it's going to be something simple, like pump seals. I think that before I did all the things you've done so far I would have swapped the head from another bay or put on my spare pump head. You've done a lot of work.
 

Jerry33

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MEP001 and Randy were right on. Swapped the pump and bingo. Everything normal. Haven't pulled the head on the malfunctioning one, but logic now says it it is the seals. Thanks guys.
 
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